1. Field of Invention
The present invention relates generally to a system and method for testing and validating the integrity of air filters, and, more particularly, to a system and method for in line in situ validation of air filters of an exhaust filter system.
2. Description of Prior Art
Cleanliness of air supplied and exhausted from containment equipment such as Biological Safety Cabinets or Bio Safety Cabinets (“BSC”), lab hoods, bag in bag out systems, etc., depend on the integrity of air filters installed to remove contaminants. Particle contaminants are typically removed by using high efficiency air filters.
Standard operating protocols require that these air filters be tested periodically to ensure that they are leak free. Typically, this validation testing requires the shutting down of the operations of the containment equipment to gain access to the filter. The integrity of the filter is verified by challenging the filter with an aerosol and checking for leaks by scanning the face of the filter. Since hazardous materials are often handled in these containment equipment, validation of filters will typically necessitate decontamination prior to accessing the filter for testing.
A manual method for testing the integrity of air filters of an exhaust filter system has been used. In the manual method, a filter is scanned with a manually movable sampling head operated via gloves mounted on the chamber. The gloves separate the outside and the operator from the contaminants inside the chamber.
As seen in FIGS. 1A-D, a current automatic scanning system for testing the integrity of air filters of an exhaust filter system is shown. Components of this scanning system for testing filters are included within the filter housing/chamber. In particular, FIGS. 1A-D show a conventional exhaust filter system 100, where contaminated air is exhausted from an exhaust duct 120 through a filter 130 housed in a plenum 110. An exhaust outlet 140 is also shown. Since all such systems 100 have an exhaust plenum 110, it is possible to use the space to install an air sampling inlet, also known as a scanning head/sampling probe 150, inside the plenum 110. This allows for scanning of the filter 130 for leaks without actually accessing the filter 130. The scan head 150 can be automatically moved in both the X and Y directions by a traditional XY coordinate system (scan mechanism) 160 or by a set of racks and pinions (not shown), which are also within the exhaust plenum 110. FIG. 1C further shows multiple sampling probes 150 coupled in a row connected to scanning arms 155, and FIG. 1D shows one large sampling cylinder 150′ with several sampling holes or slits installed within the scanning arm 155′. The sampling probes 150 and sampling cylinder 150′ are used for scanning the entire downstream face of the installed filter to determine leaks. An optical particle counter (“OPC”), and an exhaust stack tube 111 are also shown.
With respect to current automatic systems, the entire XY traverse gear is enclosed inside the plenum 110 and mounted on an XY traverse mechanism that is fixed on the inside of the back plate 115 of the inside of the plenum 110 with only the electric and sample connection leading outside via sealed grommets (not shown). When needed, the XY traverse system can be powered and the filter can be scanned.